1. Field of the Disclosure
The present disclosure relates to an accelerator-pedal reaction force control apparatus which controls a reaction force of an accelerator pedal.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2007-76468 (hereinafter referred to as Patent Document 1) discloses a technique for allowing a driver to recognize an optimum amount of operation of an accelerator pedal by increasing an operation reaction force (hereinafter simply referred to as a reaction force) of the accelerator pedal stepwise at the optimum amount of operation of the accelerator pedal, that is, an optimum accelerator opening degree, at which an optimum specific fuel consumption can be obtained.
Patent Document 1 also discloses an operation of reducing the amount of increase in the reaction force to allow the acceleration of the vehicle if the operating speed of the accelerator pedal is high.
According to the technique described in Patent Document 1, the reaction force of the accelerator pedal is increased at a certain accelerator opening degree to avoid an increase in the specific fuel consumption. However, the accelerator pedal is a main operating member operated by the driver to drive the vehicle in a way that the driver desires, and the operational feel of the accelerator pedal experienced by the driver is extremely delicate. For this reason, this type of reaction-force control apparatus, which contributes to the reduction in fuel consumption, cannot be put into practical use unless the function for reducing the fuel consumption can be achieved together with satisfactory operational feel of the accelerator pedal.
Various tests have been performed for putting the reaction-force control apparatus which contributes to the reduction in fuel consumption into practical use. As a result of these tests, it was found that when the reaction force is increased at a certain accelerator opening degree to cause the driver to recognize the increase in the specific fuel consumption, as in Patent Document 1, the amount of increase in the reaction force (amount of increase from a basic reaction force) must be set in consideration of various factors, and there is room for improvement in the method for setting the amount of increase.
Generally, the accelerator pedal has a basic reaction force which corresponds to the accelerator opening degree. When the reaction force is increased at a certain accelerator opening degree, the sum of the basic reaction force and the amount of increase in the reaction force is applied to the foot of the driver. However, even if the amount of increase in the reaction force is constant, the driver feels the increase in the reaction force differently in accordance with the state in which the accelerator pedal has been depressed before the increase in the reaction force, for example, in accordance with the basic reaction force and the manner in which the basic reaction force has been changed before the increase in the reaction force. For example, it is generally more difficult for the driver to recognize the change in force required to depress the accelerator pedal when the reaction force is increased by the same amount at the same accelerator opening degree in the case in which the accelerator opening degree is increased from an intermediate accelerator opening degree as well as the case in which the accelerator opening degree is increased from 0 degrees, such as in the case where the vehicle is started running from a stopped state. Therefore, there is a risk that the optimum amount of operation cannot be recognized by the driver.